Method and apparatus for cold drawing or rolling of metal wire rod

ABSTRACT

A method and apparatus for wire drawing using the oval-round series in which the round groove rolls are prestressed in opposite directions and the oval wire rod is then introduced into the round groove at an inclination such that the oval wire rod cooperates with the prestressed round groove rolls to produce wire rod having a desired round configuration.

United States Patent [191 Bennet [451 May 7,1974

[ METHOD AND APPARATUS FOR COLD DRAWING OR ROLLING OF METAL WIRE ROD [75] Inventor: Tom Joachim Bennet,

Smedjebacken, Sweden [73] Assignee: Morglrdehammar Aktiebohg,

Smedjebacken, Sweden [22] Filed: Sept. 8, 1972 [21] App]. No.: 287,354

[30] Foreign Application Priority Data Sept. 10, 1971 Sweden ..l1494/71 [52] U.S. Cl. 72/235, 72/247 [51] Int. Cl B211) 13/12 [58] Field of Search 72/235, 234, 231, 366,

[56] References Cited UNITED STATES PATENTS 2,369,730 2/1945 Fisk 72/235 X 3,470,722 10/1969 Woodcock et a1 72/237 2,105,258 1/1938 O'Malley 72/227 2,140,414 12/1938 Brownstein 72/235 Primary Examiner-Milton S. Mehr [57] ABSTRACT A method and apparatus for wire drawing using the oval-round series in which the round groove rolls are prestressed in opposite directions and the oval wire rod is then introduced into the round groove at an inclination such that the oval wire rod cooperates with the prestressed round groove rolls to produce wire rod having a desired round configuration.

9 Claims, 11 Drawing Figures PATENTEI] IIAY 7 I974 SIRII'Q PRIOR ART .m- FIG. IA

PRIOR ART PRIOR ART FIG. 18

FIGI

METHOD AND APPARATUS FOR COLD DRAWING R ROLLING 0F METAL WIRE ROD This invention relates to the art of wire drawing and, more particularly, to an improved method and apparatus for cold drawing or rolling of metal wire rod by utilizing the oval-round reduction series.

A reduction series very often used in wire drawing is the oval-round series in which the wire rod is first formed in a pair of rolls to oval cross section and, immediately thereafter, in subsequent roll pairs is formed to a given round cross section. With such an arrangement, the round groove rolls normally are positioned in a plane which is at an angle of 90 relative to the plane of oval groove rolls, the reason for this being that it eliminates the necessity of turning the oval shaped wire through 90, as is sometimes done in hot rolling and which requires substantial guide equipment.

The above described method of wire reduction is applied practically exclusively where wire rod drawing is accomplished with roller dies, that is, where the drawing die is replaced by a roller die" unit. The term "roller die" unit refers to a set of nondriven rolls of which the first roll pair, in the drawing direction, has oval grooves and the second roll pair has round grooves. The two roll pairs are set at an angle of 90 relative to each other but the center line of the roll path defined by the two roll pairs are aligned and coaxial.

One problem with the above-described arrangement is the instability of the oval wire rod as it enters the round groove rolls. This instability results from the play inherently present in the bearings and mountings of the round groove rolls. Due to the presence of this play, the oval wire rod entering the grooves will frequently impose forces on the rolls which will displace one roll relative to the other in opposite axial directions. The result of this displacement of the rolls is a wire rod that is more oval than round in cross sectional configuration.

While this problem can be alleviated, to some extent, by placing holders between the oval groove rolls and the round groove rolls, this solution has the disadvantage that the holder can scratch the wire rod unless it is provided with rollers which, in turn, complicates the construction. In any event, the holders do not entirely eliminate the instability of the oval wire rod as it enters the round groove rolls.

Another theoretically possible solution to this problem is to preset the round groove rolls in an axially offset manner such that the oval wire rod will coact with the round rolls to return the rolls to their proper position. However, this solution is no more than theoretical since the instability of the oval wire rod renders is impossible to predict the direction in which the forces will be imposed on the round rolls. As a result, it is entirely possible that the oval wire rod will impose axial forces on the round rolls in the same direction as the rolls are preset, thereby aggravating rather than solving the problem.

In accordance with the principles of this invention, the foregoing problem is overcome by employing a roller die unit in which the round groove rolls are prestressed in opposite axial directions and the oval wire rod is introduced into the round groove at an inclination such that the ovality of the wire rod coacts with the prestressed rolls to return the two rolls to a centered position whereby a round wire rod is produced.

A more complete understanding of the invention will be received from a complete reading of the following description which, together with the attached drawings, discloses but certain forms of the preferred embodiment of the invention.

Referring now to the drawings wherein like reference numerals indicate like parts in the various views:

FIG. 1 is a schematic illustration of a conventional prior art cold wire drawing process;

FIG. 1A is a view taken along line AA of FIG. 1;

FIG. 1B is a view taken along line 8-8 of FIG. 1;

FIGS. 2A-D are schematic graphic presentations of the problem solved by the instant invention;

FIG. 3 is a diagrammatic illustration of the displacement of the rolls relative to each other which takes place with the prior art arrangement;

FIG. 4 is a schematic illustration of one embodiment of the invention;

FIG. 5 is a schematic presentation of the cold wire drawing process using the solution of FIG. 4; and

FIG. 6 illustrates one arrangement of the rolls to achieve the solution illustrated in FIG. 4.

Referring now more in detail to the drawings, FIG. 1 illustrates a conventional roller die unit used in an oval-round series and comprises one roll pair I, 2 defining an oval groove 6 and a second roll pair 3, 4 defining a round groove 7. Roll pair 3, 4 lie in a plane that is rotated by from the plane of the roll pair 1, 2 (see FIG. 1B). The wire rod to be drawn is designated by the numeral 5. Subsequent to its forming to oval section, the wire rod is designated at 5' and subsequent to its forming to a round shape is designated at 5". FIG. 1B shows in detail how the oval and round grooves are shaped relative to each other and, as is apparent from that Figure, the center line of the roll paths through both the oval and round grooves are in alignment and coaxial.

FIGS. ZA-D illustrate the problem solved by this invention. FIG. 2A presents the desired theoretical relationship between the round groove 7 and the oval wire rod 5 as it enters the round groove. In this orientation, the major axis of the oval cross section lies in a plane which is perpendicular to the axis of each of the rolls 3 and 4.

FIGS. 25 and 2C illustrate the problem which occurs when the oval wire rod 5' enters the round groove 7 in an unstable condition. For example, FIG. 2B shows the rolls 3, 4 as being axially displaced in opposite directions which results from the oval wire rod being slightly inclined to the right as viewed in FIG. 28. FIG. 2C illustrates how the two rolls 3, 4 are axially offset in the opposite direction when the oval wire rod enters the groove 7 inclined to the left, as viewed in that Figure.

FIG. 20 schematically presents the forces that act on the rolls 3, 4 to cause axial displacement of the rolls in the manner shown in FIG. 2B. As the wire rod is introduced into the round groove rolls, the oval wire rod is subjected to a rolling pressure P, due to the height of the rod exceeding the depth of the groove 7. Where the wire rod is inclined such that its major axis is no longer perpendicular to the axis of the rolls, the wire rod is subjected to a torsional movement M,,. The movement of reaction of the wire rod consists of a torsional resistance in the wire rod and axial forces P acting on the rolls 3,4. As a result, the rolls 3, 4 will move axially in opposite directions until the play has been eliminated and the wire rod will then achieve a state of balance in which the moment of the axial forces P, and the torsional moment neutralize the moment caused by the rolling force P The inclined position of the oval wire rod and the resultant and displacement of the rolls 3, 4 then produce in the final drawn product a wire rod having an ovality corresponding to FIG. 28. It will be appreciated that should the oval wire rod be inclined in the opposite direction to that illustrated in FIG. 2D, the same force analysis applies but the rolls 3, 4 will be offset in the opposite direction in the manner shown in FIG. 2C.

The magnitude of the axial displacement of each roll depends on the play that is present in the bearings and mountings and, further, on the elasticity of the material. FIG. 3 is a graphical presentation of these factors wherein the portion above the abscissa represents the upper roll and the portion below the abscissa represents the lower roll. The movement in axial direction which any point f of any of the rolls can be displaced has been plotted along the abscissa. The points a and b indicate the total play in each direction as a function of the construction of the bearings and mountings. The elasticity of the material, as a function of the forces l has been superposed on points a and b with the total displacement, for a given force P appearing from the points a and d.

This invention proposes to solve the foregoing problem in the manner illustrated in FIG. 4. Thus, the round groove roll 3 is prestressed in one direction by a force F, while the roll 4 is prestressed in the opposite direction by a force F, so that the play normally present is taken up at each roll in the direction of the prestressing. Any suitable means, such as springs, may be used to supply the prestressing forces F and F,. In addition, the oval wire rod 5' is introduced to the round groove at an inclination. In other words, as shown in FIG. 4, the major axis of the oval is inclined a certain number of degrees from the 90 plane in which the rolls 3, 4 are normally positioned. ln this manner, the oval wire rod 5' entering the round groove rolls is given a predetermined defined position; in the case illustrated in FIG. 4, an inclination to the right. When the oval wire rod is introduced into the round groove at an inclination of up to about with the rolls being axially prestressed and offset. the coaction between the oval wire rod and the rolls results in forces which tend to move the round rolls 3, 4 back to a centered, aligned position against the prestressing and to rotate the oval wire rod back to an upright position. FIG. 5 shows the resulting relationship of the rolls and wire rod when the wire rod is fed in the manner illustrated in FIG. 4.

The desired inclined position of the oval wire rod relative to the round groove 7 can be achieved in several different ways. One way is to turn the oval groove rolls 1, 2 through an angle of 2 to 10, as shown in FIG. 6. The same result may be obtained by turning the round groove rolls through the same angle but in the opposite direction. Another method would be to incline one of the oval groove rolls, or possibly both of the rolls, so as to give the oval wire rod a helical shape. Still a further approach would be to design the oval groove 6 asymmetrically in the oval groove rolls such that the axis of symmetry of the groove forms an angle of to 10 with the plane of division of the rolls.

While the invention has been described with reference to certain specific embodiments, neither the illustrated embodiments nor the terminology employed in describing them is intended to be limiting; rather it is intended to be limited only by the scope of the appended claims.

Having described the invention, what is claimed is:

l. A method of cold drawing metal wire rod with a roller die unit by utilizing an oval-round reduction series in which the wire rod is first fed through oval groove rolls to draw the wire to an oval cross section and the wire rod is then advanced to a pair of round groove rolls arranged at an angle to the oval groove rolls, said method comprising the steps of;

prestressing one of the round groove rolls in one axial direction and prestressing the other round groove roll in the opposite axial direction before the wire rod is fed into the rolls, and

feeding the oval wire rod into the round groove rolls with the major axis of the oval wire rod inclined by up to about 10 from a plane perpendicular to the axes of the round groove rolls.

2. The method according to claim 1 wherein the step of feeding the oval wire rod at an inclination comprises positioning the oval groove rolls to assume a position which differs by up to about 10 from the conventional angle relative to the round groove rolls.

3. The method according to claim 1 wherein the step of feeding the oval wire rod at an inclination com-prises positioning the round groove rolls in a position which differs by up to about 10 from the conventional 90 angle relative to the oval groove rolls.

4. The method according to claim 1 wherein the step of feeding the oval wire rod at an inclination comprises inclining one of the oval groove rolls relative to the other so that the oval wire rod is given a helical shape.

5. A method according to claim 1 wherein the step of feeding the wire rod into the round groove rolls at an inclination includes the step of passing the wire rod through oval groove rolls in which the oval groove is formed asymetrically.

6. The method according to claim 1 wherein the inclination of the oval wire rod relative to each of the two round groove rolls is opposite to the direction of prestress of each roll.

7. Apparatus for cold drawing metal wire rod using a roller die unit comprising a pair of oval groove rolls for drawing the wire to an oval cross section and a pair of round groove rolls for drawing the oval wire rod to a round cross section, the improvement comprising;

said pair of round groove rolls being axially prestressed in opposite axial directions, and

means for feeding the oval wire rod from said oval groove rolls into said round groove rolls at an inclination such that the major axis of the oval wire rod is dis laced by up to about 10 from a plane perpendicular to the axes of said round groove rolls.

8. The apparatus of claim 7 wherein said means comprises:

said oval roove rolls being positioned in a plane which is es than perpendicular to the plane of said round groove rolls by an angle of up to about l0 with the roll path through said round groove rolls arid said oval groove rolls being aligned and coaxia 9. The apparatus of claim 7 wherei4 said means comprises:

the oval groove in said oval groove rolls being positioned such that the major axis of the oval defined by the groove is inclined by up to about l0 from the plane of said round groove rolls.

i i i l 

1. A method of cold drawing metal wire rod with a roller die unit by utilizing an oval-round reduction Series in which the wire rod is first fed through oval groove rolls to draw the wire to an oval cross section and the wire rod is then advanced to a pair of round groove rolls arranged at an angle to the oval groove rolls, said method comprising the steps of; prestressing one of the round groove rolls in one axial direction and prestressing the other round groove roll in the opposite axial direction before the wire rod is fed into the rolls, and feeding the oval wire rod into the round groove rolls with the major axis of the oval wire rod inclined by up to about 10* from a plane perpendicular to the axes of the round groove rolls.
 2. The method according to claim 1 wherein the step of feeding the oval wire rod at an inclination comprises positioning the oval groove rolls to assume a position which differs by up to about 10* from the conventional 90* angle relative to the round groove rolls.
 3. The method according to claim 1 wherein the step of feeding the oval wire rod at an inclination comprises positioning the round groove rolls in a position which differs by up to about 10* from the conventional 90* angle relative to the oval groove rolls.
 4. The method according to claim 1 wherein the step of feeding the oval wire rod at an inclination comprises inclining one of the oval groove rolls relative to the other so that the oval wire rod is given a helical shape.
 5. A method according to claim 1 wherein the step of feeding the wire rod into the round groove rolls at an inclination includes the step of passing the wire rod through oval groove rolls in which the oval groove is formed asymetrically.
 6. The method according to claim 1 wherein the inclination of the oval wire rod relative to each of the two round groove rolls is opposite to the direction of prestress of each roll.
 7. Apparatus for cold drawing metal wire rod using a roller die unit comprising a pair of oval groove rolls for drawing the wire to an oval cross section and a pair of round groove rolls for drawing the oval wire rod to a round cross section, the improvement comprising; said pair of round groove rolls being axially prestressed in opposite axial directions, and means for feeding the oval wire rod from said oval groove rolls into said round groove rolls at an inclination such that the major axis of the oval wire rod is displaced by up to about 10* from a plane perpendicular to the axes of said round groove rolls.
 8. The apparatus of claim 7 wherein said means comprises: said oval groove rolls being positioned in a plane which is less than perpendicular to the plane of said round groove rolls by an angle of up to about 10* with the roll path through said round groove rolls and said oval groove rolls being aligned and coaxial.
 9. The apparatus of claim 7 wherei4 said means comprises: the oval groove in said oval groove rolls being positioned such that the major axis of the oval defined by the groove is inclined by up to about 10* from the plane of said round groove rolls. 